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A civil war broke out soon after the military seized power in 1966

Although most of Nigeria's current population of about 170 million was not born when the country's first coup was staged 50 years ago, its legacy lingers on, writes Nigerian historian and author Max Siollun.

On 15 January 1966, a group of young, idealistic, UK-trained army majors overthrew Nigeria's democratic government in a violent military coup.

The coup leaders described it as a brief and temporary revolution to end corruption and ethnic rivalry. Instead, it made them worse.

The coup exposed the vulnerability of the Nigerian state, and how simple it was to use soldiers to attack the government, rather than protect it.

A succession of increasingly repressive military governments ruled Nigeria for 29 of the next 33 years, until the restoration of democracy in 1999. Here are four ways in which Nigeria - Africa's most populous state and leading oil producer - is still affected by the events of 1966:

Protesters in south-east Nigeria have recently demanded the region's secession from Nigeria and the formation of a new country called Biafra. The Biafra movement's origins can be traced back to the January 1966 coup.

The officers who staged the coup were mostly Christian southerners from the Igbo ethnic group, and they assassinated several northerners, including the four highest-ranking northern army officers, Prime Minister Tafawa Balewa, and Northern Region Premier Ahmadu Bello (both Muslims from the north).

Army commander Major-General Johnson Aguiyi-Ironsi, an Igbo, suppressed the coup, but seized power himself. Northerners interpreted the coup as an Igbo-led conspiracy to subjugate the north and impose Igbo domination.

Six months later, northern soldiers staged another even bloodier counter-coup against their Igbo colleagues.

Northern mobs killed around 30,000 Igbos, and Igbos fled south, and in the following year sought to form a new breakaway country called Biafra. Northerners living in Igbo areas were also killed in revenge attacks.

Although the army suppressed the attempt at secession after a brutal civil war, bitterness remains 50 years later.

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The late Emeka Ojukwu led the attempt to create a separate state in the south-east

Unaddressed grievances from 1966 lie at the heart of the Biafra movement's resurgence. Many Igbos feel that Nigeria regards them as a fifth column and is still punishing them for their previous attempt at secession.

This provision encouraged corruption and the do-or-die nature of Nigeria's elections, as winners now had control over the country's vast mineral wealth.

It is also the source of much bitterness in Nigeria's oil-producing areas, and a cause of the latent Niger Delta insurgency which rocked Nigeria for several years and severely disrupted its oil industry.

'Class of 1966'

The January 1966 coup propelled a group of young military officers onto the national stage. Now wealthy septuagenarian grandfathers, they still wield enormous influence in Nigerian politics.

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Johnson Aguiyi-Ironsi was Nigeria's first military ruler

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Olusegun Obasanjo ruled as a military general and an elected president

Gen Obasanjo is one of these retired military kingmakers. His withdrawal of support for then-President Goodluck Jonathan was one factor in his presidential election defeat last year, and the victory of current President Muhammadu Buhari.

As a young officer, Mr Buhari was among the young northern officers who in July 1966 staged the counter-coup against the Igbo majors.

The influence of retired military officers is so pervasive that Mr Jonathan is the only president in Nigeria's history who had no personal or family involvement in the 1966 crisis and the ensuing civil war.

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Muhammadu Buhari is serving his second stint as head of state

Last year, Nigeria's then-national security adviser admitted that previous governments' wariness of the coup-prone army made them reluctant to upgrade its weaponry.

Years of strategic military under-investment recently came back to haunt Nigeria when soldiers facing Islamist militant group Boko Haram complained that they were under-equipped to fight the insurgents.

This coup issue also partly explains why Nigerian authorities react with such severity to any disobedience by soldiers.

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Troops have been battling to end Boko Haram's six-year insurgency

Yet, ironically, Nigeria partially owes its continued existence to the near obsessive desire to avoid a repeat of the 1966 bloodshed.

The young military firebrands have mellowed and talk their way out of crisis rather than blasting their way into it.

The elaborate power-sharing arrangements in Nigeria's constitution, and the unwritten rule requiring rotation of political power between the north and south are legacies of the mistrust engendered in 1966.

Nigeria has matured. So have its former coup leaders.

* Max Siollun is a Nigerian historian, writer, and author of the books Oil, Politics and Violence: Nigeria's Military Coup Culture 1966-1976 and Soldiers of Fortune: a History of Nigeria (1983-1993).